@mixin scrollbars($size, $foreground-color,
    $background-color: mix($foreground-color, white,  50%),
    $hover-color: mix($foreground-color, white, 25%),
    $border-color: rgba(0,0,0,0)
) {
    @if (lightness($background-color) < 50) {
        // For Firefox
        scrollbar-color: $foreground-color $background-color;
    }
}